What is the difference between Audi A6 C8 and C7?

I am looking to buy a used Audi A6, but am confused by the different model codes. Can someone explain the difference between the C8 and C7 models?

The main difference between the C8 and C7 Audi A6 models is the design. The C8 has a sleeker, more modern look compared to the C7.

Performance-wise, the C8 has upgraded engines and transmission compared to the C7. With the C8, you can expect smoother and more powerful driving experience.